The invention relates to a method for controlling the rotational speed of a rotary blood pump having a design rotational speed at which minimal detachment and swirling of the blood flow occur.
In EP 0 961 621 B1 (Impella) an intravascular blood pump is described which is inserted through the vascular system into the body and placed in the heart or at any other location where blood is intended to be pumped. The blood pump comprises a housing with a diameter of 5.4 to 6.4 mm which defines the stator of a motor. A rotor is connected with an impeller which rotates in a pump ring. This very small blood pump has a relatively high rotational speed in the range of 30,000 rpm.
In EP 0 925 080 B1 (Impella) a method for controlling a rotational speed of a blood pump is described, wherein the blood pump comprises pressure sensors for determining the pressure difference prevailing at the blood pump. The rotational speed of a motor is controlled in accordance with the signals supplied by the pressure sensors. Thus, a desired volume flow is generated which ensures the desired pumping action.
Continuously delivering rotary pumps have a so-called design rotational speed. The impeller advancing the blood is shaped such that at the design rotational speed flow detachments at the impeller blades are minimized, or, ideally, no flow detachments occur at all. Thus, a low-turbulent flow is obtained. Flow detachments and turbulences involve the risk of thrombogenesis, wherein blood accumulates and gathers at the impeller or at other locations in the blood system. This impairs the operation of the impeller. Further, this involves the risk of obstructions in the blood system.